Method of dutching cocoa

ABSTRACT

The dutching of cocoa to obtain a product of rich homogeneous color and high sterility is accomplished by grinding a pressed cake made from cocoa beans, converting the ground mass into a coarse, free-flowing powder, mixing the powder with sufficient aqueous alkaline solution and desired additives to obtain a damp mass containing about 20-35 wt. per cent moisture and feeding this mixture into a combined cooker and pressurized extruder and then pelletizing the cooked composition. The pellets are formed by extruding the mass through appropriate dies and breaking off the rods to form pellets by interaction with a stationary plate. The preferable temperature range of the combined cooking-pressurizing step is 150°-230° F. and the preferred pressures are progressive to between 500 and 1300 pounds per square inch adjacent the extruding die. The pellets are optionally dried in a continuous fashion by a plurality of gas jet streams that lift and tumble the pellets continuously passing underneath on a vibrating conveyor.

REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.443,517, filed Feb. 19, 1974 now U.S. Pat. No. 3,868,469, issued Feb.25, 1975, which in turn is a continuation-in-part of application Ser.No. 253,839, filed May 16, 1972, now abandoned.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The present invention relates to the treatment of cocoa, and moreparticularly, to an improved method and system for dutching of cocoa forattaining a rich color, improved flavoring and other favorableparameters.

Heretofore, the process of dutching of cocoa has been a relatively longand expensive proposition. Basically, the same batch process wherein thecocoa is treated in large cooking vats has been used for at least 100years without significant improvement. In most prior art processes,after roasting the beans and removing the husk or shell, the brokenpieces of the beans, commonly referred to as the nibs, are crushed orground to break the cells and form a smooth, creamy paste, known aschocolate liquor. Next the liquor is fed a hydraulic press whereby withthe proper timing, temperature and moisture control and removal of aportion of the fat or cocoa butter, a press cake is formed. Typically,the press cake is next broken up and mixed with an alkalizing solutionin the batch pressure cooker. The cooker then converts to a vacuum dryerto reduce the moisture content in the batch. The contents of the vat arethen deposited in drums or other suitable containers for several daysand allowed to cool. The cooled mass is then ground to a fine powderthat can be used in devil's food cake, chocolate drinks, chocolate icecream and chocolate cookies.

The standard batch process of the prior art suffers from severalshortcomings. First, the conditions of treatment from batch to batchmust be rigidly maintained in order to obtain proper moisture, pH, andlow microbial flora content and uniformity of flavor and color. By thevery nature of the non-continuous process, this has been found to beextermely difficult to do and requires the constant monitoring of peopleand machines. Secondly, the vat cooking and drying of the batch and theabsence of significant mechanical working result in nonuniformity ofheating of the cocoa so that parts are scorched and other parts areundercooked, giving a nonuniform product in terms of color and taste.The color obtained in the batch process is not as dark and rich in colorwith the same amount of alkali that is desired in many commercialproducts. In addition to requiring additional equipment and people tomaintain the proper conditions, the large vats further financiallyburden the processor since the space required to house the equipment issubstantial.

Problems of the prior art batch drying processes have resulted whenprevious attempts to depart from the above procedure have been made.First the danger of charring has arisen when the drying process has beenattempted to be accelerated by employing a higher temperature. The priorprocesses have not included a necessary volume of working gas todistribute the heat to the end product efficiently and uniformly. Theproblem of case hardening of the individual cocoa solids is also anemesis in the prior processes. This arises when the temperature of theproduct solid rises too rapidly thereby hardening the outer surface ofthe product. It is caused, in part at least, by not providing suitablysmall sized product solids, controlled heat, and large volume gas flow.Grinding and regrinding of the hardened solids thus becomes a tryingnecessity in an attempt to gain a satisfactory product.

In the past, the above overall "batch method" has been attempted to bereplaced by a continuous method. Such attempts have, however, beenunsuccessful and exemplary of those known in this art is shown by theU.S. Pat. to Walker No. 1,167,959. The failure of the continuousprocesses has keyed on the inability to find a way to successfully formthe mixture of cocoa material and alkaline solution and cook the sameand the failure to devise a method for efficiently drying and coolingthe cocoa end product in a continuous manner.

A more recent process for preparing dutched cocoa may be found in U.S.Pat. No. 3,754,928, a patent issued on Aug. 28, 1973, or subsequent tothe filing of applicant's parent application. This patent discloses amethod for dutching cocoa by subjecting an aqueous alkaline solution ofcocoa to frictional and compressive forces to rapidly raise itstempeature to 200-300° F. within about 10 seconds and maintaining thistemperature for about 45 to 75 seconds prior to cooling. The patentdiscloses that the frictional and compressive forces may be applied byextrusion of the mixture through a die. The mixture initially containsabout 4 to 6 parts by weight of water and after drying contains about 4parts by weight of water. However, this process requires hightemperatures and careful control of temperatures and residence times inpassing the mixture through the die as well as intense initialpressurization. Moreover, the low initial moisture content isdetrimental to good working of the mixture because 4 to 6 parts of watersaturated with alkali is an insufficient amount of liquid to wet out allparticles of cocoa subject to frictional and compressive forces. Theconsequences of incomplete wetting is incomplete chemical reaction andunequal distribution of the alkali used. Therefore, because of this,poor control of production of varieties and intensities of color in thecocoa as well as in the finished product in which the cocoa is theresult.

A second recently issued patent, U.S. Pat. No. 3,778,519, teaches thatin the impregnation of cocoa seeds with alkali or water and eventualsterilization, requires that the moisture content be kept as low aspossible because of subsequent difficulties in drying. The presentinvention provides a procedure where outstanding results are obtainedusing high initial moisture contents. Accordingly, the method of thepresent invention represents improvements in the art of dutching cocoa.

OBJECTIVES OF THE INVENTION

Thus, it is one object of the present invention to provide an improvedmethod of dutching of cocoa that is continuous and results in improvedcolor in an infinite variety of shades and tones and other favorableparameters of the end product.

It is another object of the present invention to gain maximum colorusing the legal amounts of alkali.

It is another object of the present invention to provide a process fordutching cocoa that is considerably faster, takes up less room in aplant for the processing equipment and is more economical to operate andproperly control.

It is another object of the present invention to provide a continuousdutching process that gives uniform cooking of the cocoa withoutscorching or undercooking the product.

It is still another object of the present invention to provide acontinuous dutching process wherein the product is under continuousmechanical working during premixing and cooking.

It is still another object of the present invention to provide a processfor dutching cocoa wherein pellets of the finished product are dried andcooled by jet streams impinging on a moving bed to lift and tumble thepellets.

It is still another object of the present invention to produce afinished product that is virtually sterile.

It is still another object of the present invention to fully gelatinizethe product so as to produce a better suspension of cocoa when used incocoa drinks.

BRIEF DESCRIPTION OF THE INVENTION

According to the present invention, the cocoa material, such as aprepared press cake or nibs, is pulverized while at the same time anaqueous alkaline solution is being prepared in a separate tank. Thepowdered material and the solution are combined and subjected tovigorous mechanical working to form a homogeneous resultant productmixture. Immediately after this premixing step has been completed, theproduct mixture is placed in a combination cooker-extruder where it iscontinuously cooked under pressure and mechanically worked to furtherobtain uniformity of product. The cooker-extruder is preferably of anauger type wherein the pitch of the auger gradually decreases toward thedischarge end to progressively subject the mixture to greater andgreater pressure. This compression of the product mass permits efficientextruding through suitable die means positioned directly on the enddischarge face of the cooker and to form a product rod that is readilydivided into pellet size lengths. Drying of the pellets takes place inaccordance with the invention on a fluidized bed by a plurality of jetstreams that lift and tumble the pellets in an inert atmosphere.

The premixing of the ground press cake with the alkaline solutionenhances the interaction between the molecules within the productmixture to gain the desired color and also leads to a more homogeneousproduct mixture for reaction in the cooker-extruder to produce a moreuniform color and taste. The mechanical working during the cooking stepis also of great importance since the molecules of the mixture areconstantly being stirred and mixed to prevent scorching andundercooking. Preferably, the cooking is performed in the range ofapproximately 150-230° F. while the pressure maintained in the finalstages of pressurization is between approximately 500-1300 pounds persquare inch.

The drying and cooling steps are of substantial importance since it ispossible for the first time insofar as I am aware to rapidly dry cocoaproduct without the previous hazards, such as scorching and degradingthe flavor or color, and then drastically cool the product. However, foruses in certain areas the drying step may be omitted and the productused in the form exiting the extruder. The 20-35 percent total moisturecontent of the material at the entrance to the premixer is reduced toapproximately four percent at the end of the drying and cooling steps.The 20-35 percent moisture content has been found to provide an easilyworkable mixture and one conducible to forming a homogeneous mass and tobe particularly suited to causing the rod to be easily broken by actingagainst a stationary plate as it leaves the die means of the extruder.The 20-30 percent moisture content has also been found to provide aproduct which has a rich homogeneous color and to provide a product ofhigh sterility. In some cases, notably with the fat content in the rangeof 10 to 12 percent, the moisture may be reduced to the neighborhood of27 percent and no plate is needed to effect breaking off to form thepellets. The pellets, being in lengths of approximately 1/4 to 1 inchlong and the rod being approximately one-eighth inch in diameter, giveexcellent drying action. The drying is carried out in an inertatmosphere in the temperature range of 350-450° F. for approximately 2.5to 3 minutes. The inert atmosphere may be any of the well known inertgases, e.g. nitrogen, argon, etc. as well as any gas which would notreact with or affect the product. In the continuous procedure, air whichhas been burned to consume all the oxygen compounds and thus consistsprimarily of nitrogen, is suitable. The drastic cooling step lowers thetemperature to approximately the ambient temperature in the same lengthof time.

Still other objects and advantages of the present invention will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein I have shown and described only thepreferred embodiment of the invention, simply by way of illustration ofthe best mode contemplated by me of carrying out my invention. As willbe realized, the invention is capable of other and differentembodiments, and its several details are capable of modification invarious obvious respects, all without departing from the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The steps of the process begin with the grinding of a press cake thathas been formed in a press from roasted cocoa beans. While use of apress cake of cocoa is preferred as the starting material, it is obviousthat other cocoa forms such as nibs may also be used. However,regardless of the physical form at this stage it is subsequentlypulverized and formed into a homogeneous mass. The press cake is thenground in a conventional grinder and pulverized into a coarse,free-flowing powder. Sufficient size reduction is attained that theresultant particles will be easily workable and will pass through thedie. A preferred particle size is one in which the particles have adiameter of about one-eighth inch or less. Thus, it should be understoodthat the particles need only be ground so that they will subsequentlypass through the die without plugging the opening. It is usuallypreferred to effect grinding until the particles will pass through asuitable screen. As to the screen through which the particles arepassed, it is preferably of such size to provide particles having a sizeof about 50 to 150 mesh. The resulting powder is then passed through amagnet grate to remove any small metal particles that may have escapedprevious cleaning steps. The ground cocoa material is then stored untilmixed with alkali solution. The preferred fat content of the cocoa isabout from 0 to 16 weight %.

An aqueous alkaline solution is prepared in accordance with acceptedpractice using compounds of alkali and alkaline earth metals. A suitablealkali compound, such as sodium hydroxide, sodium carbonate (soda ash),sodium bicarbonate (NaHCO₃), potassium carbonate, potassium hydroxide,potassium bicarbonate, ammonium carbonate, ammonium bicarbonate,ammonium hydroxide, ammonia gas, magnesium carbonate, magnesium oxide,and mixtures thereof may be used. The alkaline solution should have aconcentration of about 3 to 12 weight percent, and preferably about 5 to12 weight percent. The solution is well mixed and then diluted asnecessary with water. Dilution should be sufficient to provide a maximumof 3% anhydrous K₂ CO₃ or its alkaline equivalent in the final product.With low fat nibs, up to 6 percent alkali can be present. Supplementalcolors, sugars, malts or the like may also be added at this stage. Thealkaline solution additive is then mixed with the proper proportion ofpowdered cocoa material and good mixing achieved. At this stage themixture shoud have a moisture content of about 20-35 weight percent.

The resulting damp mass or mixture is then subjected to continuousmechanical working. Mixing may be effected using one or more rotatingshafts with mullers, paddles and ribbons mounted on the shafts forthoroughly mixing the product mixture into a homogeneous state. This isparticularly advantageous since upon next entering the cooking step, thecooking may thus be performed in a uniform manner without creating hotspots or uncooked portions that might otherwise result due to anon-homogeneous mixture. A suitable piece of equipment to perform thisstep is a "Double Shaft Continuous Mixer" manufactured by Paul O. Abbe,Inc. of Little Falls, New Jersey. While this is the preferred manner ofcarrying out this step of the process it is to be understood that anytype of mechanical working can be utilized, it being only necessary thatthe mixture be subjected to such thorough mixing that a homogeneous masswill be provided prior to the cooking step.

The product mixture is now ready to enter the next important step of theprocess of the present invention. This step continues the mechanicalworking of the product mixture and concurrently cooks the mixture underpressure that progressively increases. The preferred equipment used isthe cooking extruder manufactured by The Bonnot Company of Kent, Ohio,although it is to be understood that equivalent equipment may beutilized in accordance with the broad aspects of the invention. In thepreferred equipment, the increase in pressure is provided by a variablepitch screw. It should be understood that other types of mechanicalworking may be used within the extruder. Suffice it to say that theproduct mixture is continuously worked by the screw and is progressivelypressurized while at the same time being heated to cook the product. Theexit end of the extruder is provided with an extruding die head fromwhich the compressed product mass is extruded. The extruding step formsa product rod that is divided into relatively short lengths to formproduct pellets.

In the cooker-extruder, the temperature is maintained at about 150° to230° F., preferably about 180° to 212° F., while progressivelyincreasing the pressure to a final stage of pressurization of about 500to 1300 pounds per square inch, preferably about 700 to 1100 psig. Ingeneral, the homogeneous mixture is heated substantially by thefrictional forces or mechanical working taking place within the extruderwhich can operate adiabatically but additional heating means is providedif it is necessary to maintain the indicated temperature range.Temperatures above those indicated may result in charring of theproduct.

The residence or cooking time within the cooker-extruder will vary overa limited range with limitations being placed thereon by the size of thedie opening and the speed of the screw. Suitable die openings range fromapproximately 0.100 inch to about 1.150 inch. Larger opening may be usedbut the product quality and economies of operations may be adverselyaffected. Much larger openings would also be unsuitable because therequired pressures could not be produced. In general, it may be statedthat in operation of a continuous process with continuous introductionof cocoa material, for a die having a diameter ranging from about 0.100inch to about 0.150 inch, the cooking or residence time can range fromabout two and one-half nimutes to about five minutes. A preferredresidence or cooking time within the cooker-extruder is about four tofive minutes. The time within the cooker is important, the time withinthe die being only about one second or less.

The head of the extruder includes any number of suitable extruding diesor passageway out of which come the lengths of product rod. Thecomposition of the product is gauged by moisture content of about 20-35weight percent, preferably about 27-33 percent, in order to facilitatebreaking off of the rod cleanly as it leaves the extruder head. Thisbreaking off process is facilitated by providing a stationary plateacross the path of the exiting rod. The plate breaks the rod intopellets.

At this stage the pellets may be used as desired or they may be dried byany desired process. A particular method of drying is disclosed herein.Prior to drying, the pellets still contain about 85-97 percent of theinitial water added to the press cake.

In the preferred drying procedure the pellets are dried in a fluidizedbed dryer and cooler unit wherein a bed of the pellets if formed bydirecting a plurality of downwardly extending streams of heated gas intoa bed to lift and tumble the pellets. The gas is preferably an inert gassuch as nitrogen or argon. The jet streams of gas are provided from aheating plenum and a cooling plenum or other desired source. The bed ofpellets may be oscillated or vibrated in order to effect feeding alongin a continuous fashion. At the exit end of the dryer, the dried andcooled pelletized end product is recovered for further processing andforwarding to the converter or maker of the final cocoa product. Aparticular fluidized bed dryer is sold as the "Jetzone" and manufacturedby Wolverine Corporation, Methuen, Massachusetts. Other equivalenteuipment may also be used of course.

Thus having described the equipment and the steps of the process, a moreparticular example of the process and the results can be set forth inthe following Example. Particular attention should be directed in thisExample to the operating conditions placed on the equipment that greatlyenhance the efficiency and desired results of the process.

EXAMPLE

Cocoa material in the press cake form was obtained having preferably 10to 16 percent fat. The press cake was comminuted through a pulverizer orgrinder so as to form the product into a coarse, free-flowing powder ofsufficiently small size that it would not plug the one-eighth inch dieopening. A particle size of about 60 mesh was suitable. The powder wasmetered into a mixer at a rate of approximately 972 grams per minute. Afinal diluted solution of 22.35 grams of anhydrous sodium ash (Na₂ CO₃)in 390 grams of water was prepared and fed into the mixer at apredetermined rate to give a 33 percent moisture basis. The mixer wasoperated in a continuous fashion to completely combine and mix the sodaash solution with the powdered cocoa material, and the resultanthomogeneous product mixture was then introduced into the cookingextruder at a continuous rate. Temperatures within the extruder werecontrolled in the range at 190° F. and the pressures were progressivelyincreased and in the final stage were controlled to 900 pounds persquare inch. The product was thus continuously mechanically worked by anauger as the cooking was carried out. Total time within thecooker-extruder was four and one-half minutes. The compressed productmass was continuously fed from the extruding head and formed intoapproximately one-eighth inch diameter rods as the mass was extrudedthrough the one-eighth inch die holes. This rod contained approximately29 percent moisture; a loss of 4 percent moisture occurring as the rodemerges from the extruder 40. This moisture content allowed the rod tobe freely broken into the pellets by the presence of a stationary plate.

The pellets formed were from 1/4 inch to 1 inch in length. Because ofthe control of the moisture content and the equipment used, there was noneed to employ a cutter in order to cut the rod. These pellets wereparticularly suitable for drying and cooling because of the largesurface area exposed to the gas of the fluidized bed unit.

The plenum of the fluidized bed unit was provided with a heated inertgas (nitrogen) that was injected into the bed of pellets in the dryingsection to lift and tumble the pellets for approximately 2.5 to 3minutes as the bed moved continuously along a support. The heatingelement raised the temperature and maintained the same in the range of350° to 450° F. Finally, the pellets were cooled to about ambienttemperature under the gas nozzles in about 2.5 to 3 minutes. The producthad a rich dark color and a moisture content of about 4 weight percent.

In summary, dutching of cocoa is performed by grinding the pressed cakemade from cocoa beans, converting to powder, mixing with alkalinesolution, and cooking the product mixture under pressure and continuousmechanical working. The compressed product of critical moisture ispassed through die means to form pellets by breaking into relativelyshort lengths. The drying and cooling of the pellets is performed in anefficient manner on a fluidized bed with the pellets being lifted andtumbled by downwardly directed jet streams of inert gas.

In the process of this application the initial moisture content,preliminary mixing to a homogeneous mass and residence time within thecooker-extruder are especially critical in order to provide a finalcocoa product having a rich homogeneous color, improved flavor and highsterility. By use of the term "rich color" is meant a dark uniform colorwhether brown, red or black.

In this disclosure, there is shown and described only the preferredembodiment of the invention, but, as aforementioned, it is to beunderstood that the invention is capable of use in various othercombinations and environment and is capable of changes or modificationswithin the scope of the inventive concept as expressed herein.

What is claimed is:
 1. The method of dutching cocoa so as to attain arich color and other favorable parameters in the end product, whichcomprises the steps of:combining a pulverized free-flowing powder ofcocoa material with an aqueous alkaline solution having a concentrationof about 3 to 12 weight percent, to form an initial product mixture inthe form of a damp mass, said mass having a moisture content of about 20to 35 weight percent and a maximum of up to about 6 weight percentalkaline equivalent to potassium carbonate to form a homogeneous productmixture; cooking the product mixture at a temperature of about 150-230°F. for a residence period of about two and one-half to five minuteswhile continuing mixing and while progressively increasing the pressureto a final stage of pressurization of about 500-1300 pounds per squareinch to form a heated and pressurized mass, wherein cooking is performedby feeding the product mixture into a chamber containing means to formthe product mixture into a working mass corresponding to said chamber,providing progressively greater pressure on said working mass as themixture moves from the entrance end of the chamber to the exit end, andcontrolling the heating in said chamber to raise the temperature of theproduct mixture to cooking temperature; extruding the resultant heatedand pressurized mass through die means to form a product rod, whereinthe step of extruding the product mass is carried out at the exit end ofthe elongated chamber immediately after pressurized cooking of theproduct mixture by passing the product mass through an extruding diehaving at least one restricted opening to form the product in the formof a rod, said rod product containing about 85-97 weight percent of themoisture content of the initial product.
 2. A method according to claim1 which includes the additional step of dividing the product rod intolengths to form pellets.
 3. The method of dutching cocoa according toclaim 2 wherein the step of dividing the product rod is performed bymoving the product rod from the die means directly into the path of astationary plate that bends the rod and causes breaking into lengths ofapproximately one-quarter to one inch.
 4. A method according to claim 1which includes the additional step of drying said product.
 5. A methodof dutching cocoa according to claim 1 wherein the temperature duringthe cooking step is maintained in the range of approximately 180° to212° F. and the pressure is maintained in the finals steps ofpressurization in the range between about 700 to 1100 pounds per squareinch.
 6. The method of dutching cocoa according to claim 5 wherein thecombining step of the aqueous alkaline solution with the pulverizedmaterial is carried out to give a product mixture of about 27-33 weightpercent total moisture content.
 7. The method of dutching cocoaaccording to claim 6 wherein the fat content of the cocoa material isbetween 0 percent and 16 percent by weight.
 8. The method of dutchingcocoa according to claim 1 wherein the alkaline solution contains sodiumcarbonate as the alkali, the initial moisture content is about 33percent by weight, the temperature within the cooker-extruder is about190° F., the final pressure is about 900 psig., the residence timewithin the cooker-extruder is about 41/2 minutes and the diameter of thedie opening is about 1/8 inch.